tansy ragwort
Jacobaea vulgaris Gaertn.

Overview

Appearance

Jacobaea vulgaris is a biennial to short lived perennial herb native to Eurasia. Plants can reach 1-4 ft. (0.3-1.2 m) tall.

Foliage

The leaves of the basal rosette have petioles, cauline (stem) leaves are sessile and both are deeply lobed and alternate. The leaf lobes are oblong and web-shaped. The margins of the leaves are dentate. The leaves can measure between 1.5-8 in. (4-20 cm) long and 0.75-2.25 in. (2-6 cm) wide. The leaf is medium green above, lighter underneath and occasionally tomentose.

Flowers

Flowering occurs in summer to early fall, when numerous yellow, daisy-like flowers develop in a flat topped inflorescence at the apex of the stems. Flower heads are 0.8 in. (2 cm) in diameter.

Fruit

Fruit are small and have a persistent ring of white hairs (pappus) attached. 60,000-70,000 seeds produced per plant. Seeds can remain viable for up to 15 years.

Ecological Threat

J. vulgaris invades rangelands in the West where it is toxic to livestock. In the East it invades pastures, open forests, swamps, riverbeds, coastal grasslands and disturbed areas. It was first reported in the United States in the early 1900’s. It is native to most of Europe, North Africa and western Asia and may have been introduced into the United States as a medicinal plant.

Selected Images

Maps

Invasive Listing Sources

• Alberta Weed Control Act
• California Invasive Plant Council
• California Noxious Weeds
• Colorado Noxious Weeds
• Connecticut Invasive Plant List
• Connecticut Invasive Plant Working Group
• Connecticut Noxious Weeds
• Idaho Noxious Weeds
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Massachusetts Invasive Plants Advisory Group List
• Massachusetts Noxious Weeds
• Massachusetts Prohibited Plant List
• Montana Noxious Weeds
• Native Plant Society of Oregon, 2008
• New Invaders of the Northeast and Northcentral
• Oregon Noxious Weeds
• Pacific Northwest Exotic Pest Plant Council, 1998
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States

References